Nick, when you say downwind approaches use no more power than zero wind approaches, are you comparing a shallowed, extended downwind approach to a normal zero wind approach?
Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
Final question, after all this discussion about downwind operations, I looked at the H/V charts and noticed that they go down to zero airspeed, not negative ones. Is this common? Why (not)?
Thanks,
Matthew.